1 //===----------------------------------------------------------------------===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 9 #ifndef _LIBCPP___RANDOM_EXPONENTIAL_DISTRIBUTION_H 10 #define _LIBCPP___RANDOM_EXPONENTIAL_DISTRIBUTION_H 11 12 #include <__config> 13 #include <__random/generate_canonical.h> 14 #include <__random/uniform_real_distribution.h> 15 #include <cmath> 16 #include <iosfwd> 17 #include <limits> 18 19 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 20 #pragma GCC system_header 21 #endif 22 23 _LIBCPP_PUSH_MACROS 24 #include <__undef_macros> 25 26 _LIBCPP_BEGIN_NAMESPACE_STD 27 28 template<class _RealType = double> 29 class _LIBCPP_TEMPLATE_VIS exponential_distribution 30 { 31 public: 32 // types 33 typedef _RealType result_type; 34 35 class _LIBCPP_TEMPLATE_VIS param_type 36 { 37 result_type __lambda_; 38 public: 39 typedef exponential_distribution distribution_type; 40 41 _LIBCPP_INLINE_VISIBILITY 42 explicit param_type(result_type __lambda = 1) : __lambda_(__lambda) {} 43 44 _LIBCPP_INLINE_VISIBILITY 45 result_type lambda() const {return __lambda_;} 46 47 friend _LIBCPP_INLINE_VISIBILITY 48 bool operator==(const param_type& __x, const param_type& __y) 49 {return __x.__lambda_ == __y.__lambda_;} 50 friend _LIBCPP_INLINE_VISIBILITY 51 bool operator!=(const param_type& __x, const param_type& __y) 52 {return !(__x == __y);} 53 }; 54 55 private: 56 param_type __p_; 57 58 public: 59 // constructors and reset functions 60 #ifndef _LIBCPP_CXX03_LANG 61 _LIBCPP_INLINE_VISIBILITY 62 exponential_distribution() : exponential_distribution(1) {} 63 _LIBCPP_INLINE_VISIBILITY 64 explicit exponential_distribution(result_type __lambda) 65 : __p_(param_type(__lambda)) {} 66 #else 67 _LIBCPP_INLINE_VISIBILITY 68 explicit exponential_distribution(result_type __lambda = 1) 69 : __p_(param_type(__lambda)) {} 70 #endif 71 _LIBCPP_INLINE_VISIBILITY 72 explicit exponential_distribution(const param_type& __p) : __p_(__p) {} 73 _LIBCPP_INLINE_VISIBILITY 74 void reset() {} 75 76 // generating functions 77 template<class _URNG> 78 _LIBCPP_INLINE_VISIBILITY 79 result_type operator()(_URNG& __g) 80 {return (*this)(__g, __p_);} 81 template<class _URNG> result_type operator()(_URNG& __g, const param_type& __p); 82 83 // property functions 84 _LIBCPP_INLINE_VISIBILITY 85 result_type lambda() const {return __p_.lambda();} 86 87 _LIBCPP_INLINE_VISIBILITY 88 param_type param() const {return __p_;} 89 _LIBCPP_INLINE_VISIBILITY 90 void param(const param_type& __p) {__p_ = __p;} 91 92 _LIBCPP_INLINE_VISIBILITY 93 result_type min() const {return 0;} 94 _LIBCPP_INLINE_VISIBILITY 95 result_type max() const {return numeric_limits<result_type>::infinity();} 96 97 friend _LIBCPP_INLINE_VISIBILITY 98 bool operator==(const exponential_distribution& __x, 99 const exponential_distribution& __y) 100 {return __x.__p_ == __y.__p_;} 101 friend _LIBCPP_INLINE_VISIBILITY 102 bool operator!=(const exponential_distribution& __x, 103 const exponential_distribution& __y) 104 {return !(__x == __y);} 105 }; 106 107 template <class _RealType> 108 template<class _URNG> 109 _RealType 110 exponential_distribution<_RealType>::operator()(_URNG& __g, const param_type& __p) 111 { 112 return -_VSTD::log 113 ( 114 result_type(1) - 115 _VSTD::generate_canonical<result_type, 116 numeric_limits<result_type>::digits>(__g) 117 ) 118 / __p.lambda(); 119 } 120 121 template <class _CharT, class _Traits, class _RealType> 122 basic_ostream<_CharT, _Traits>& 123 operator<<(basic_ostream<_CharT, _Traits>& __os, 124 const exponential_distribution<_RealType>& __x) 125 { 126 __save_flags<_CharT, _Traits> __lx(__os); 127 typedef basic_ostream<_CharT, _Traits> _OStream; 128 __os.flags(_OStream::dec | _OStream::left | _OStream::fixed | 129 _OStream::scientific); 130 return __os << __x.lambda(); 131 } 132 133 template <class _CharT, class _Traits, class _RealType> 134 basic_istream<_CharT, _Traits>& 135 operator>>(basic_istream<_CharT, _Traits>& __is, 136 exponential_distribution<_RealType>& __x) 137 { 138 typedef exponential_distribution<_RealType> _Eng; 139 typedef typename _Eng::result_type result_type; 140 typedef typename _Eng::param_type param_type; 141 __save_flags<_CharT, _Traits> __lx(__is); 142 typedef basic_istream<_CharT, _Traits> _Istream; 143 __is.flags(_Istream::dec | _Istream::skipws); 144 result_type __lambda; 145 __is >> __lambda; 146 if (!__is.fail()) 147 __x.param(param_type(__lambda)); 148 return __is; 149 } 150 151 _LIBCPP_END_NAMESPACE_STD 152 153 _LIBCPP_POP_MACROS 154 155 #endif // _LIBCPP___RANDOM_EXPONENTIAL_DISTRIBUTION_H 156